Inertia operated sear block



R. T. CATLIN ETAL 3,041,615

INERTIA OPERATED SEAR BLOCK July 3, 1962 Filed Aug. 17, 1960 3 Sheets-Sheet 1 i TI .Y

INVENTORS. @05527 2' 6472/ A A'WTfi/V M 2550 mam July 3, 1962 R. T. CATLJN ETAL 1, 1

INERTIA OPERATED SEAR BLOCK Filed Aug. 17, 1960 3 Sheets-Sheet 2 "i Wail July 3, 1962 R. T. CATLIN ETAL 3,041,615

INERTIA OPERATED SEAR BLOCK 5 Sheets-Sheet 3 Filed Aug. 17, 1960 F/G.7 F768 VENTORS. #055? 2 647; //V

United States Patent are Filed Aug. 17, 1960, Ser. No. 50,179 7 Claims. (Cl. 144.5)

This invention relates to powder actuated tools, and more specifically to powder actuated tools of the type in which a propellent powder loaded cartridge is exploded, to provide the driving power to seat a stud, pin or fastener, in concrete, structural steel or other penetrable construction material.

Certain of such tools are provided with means for cocking a spring urged cartridge firing striker, as a function of the manual forcible application of the tool to the work surface into which a fastener is to be driven, and with sear means to manually release said striker when the operator desires to drive the fastener. Such a fire control mechanism is shown, for example, in Patent No. 2,719,300, and the specific mechanism to which this invention may be applied is shown in the patent application of Walker, Reed. and Catlin, Serial No. 517,192,

filed June 22, 1955. In such tools, the pressure on the striker spring is released whenever the pressure applying the tool to the work is released.

The tools discussed in the .preceding paragraph are ordinarily incapable of being fired until the tool has been applied to the work surface with considerable force and ordinarily require in addition the manual operation of a safety device and the manual pulling of a trigger to permit firing. In spite of these precautions, however, there have been instances in which the dropping of such a loaded tool from a scaffold has supplied the force necessary to cockthe strikerspring and the resulting jar has in some way circumvented the requirement for manual actuation of safety and trigger. Since the parts which must be moved to effect such a cocking of the striker are all of considerable inertia, such drop firing may result if the tool is dropped either muzzle downward or muzzle upward upon a hard surface. Drop firing as a result of dropping with the axis of the barrel parallel to the surface upon which it impacts is unknown with those tools which require forcible application to the work surface to cock the striker spring.

'The principal object of this invention is to provide means which will positively prevent the firing of such tools as a result of being dropped or by any other means applying inertia forces to the tool.

We contemplate that the most effective means of defeating the inadvertent firing of such tools as a result of inertia is to harness the forces of inertia to prevent such action. inertiamember which'floats in a normal position of rest in which it does not interfere with manual operation of the fire control means but which under the urging of inertia forces severe enough to cock the striker spring will shift automatically to a position which will block the movement of the sear to a striker releasing position.

A preferred embodiment of our invention is described in the following specification, referring to the attached drawing in which:

FIG. 1 is a longitudinal sectional view through a tool embodying our invention.

FIG. 2 is a fragmentary side elevational view of the tool, partially in section, to .show the operation of the action bar and sear.

'FIG. 3 is a cross-sectional view, taken along the line 33 in FIG. 1.

Accordingly, we propose to provide an FIG. 4 is a cross-sectional view, taken along the line 4-4 in FIG. 1.

FIG. 5 is a partial longitudinal sectional .view taken the line 5-5 in FIG. 4. p

FIG. 6 is a partial exploded perspective view, showing the key elements of our invention.

FIG. 7 is a diagrammatic view, showing the key elements of our invention in a normal position of rest.

FIG. 8 is a view similar to FIG. 7, showing the tool cocked and ready to fire.

FIG. 9 is a view similar to FIG. 7, showing the parts in the position they would occupy if the tool had been cocked as a result of being dropped muzzle doum.

FIG. 10 is a view similar to FIG. 7, showing the parts in the position they would occupy if the tool had been cocked as the result of being dropped handle down.

Referring to the drawing, it will be noted that the basic tool illustrated is that shown in the co-pending application above referred to. The basic structure of such a tool comprises a barrel 1, a frame plate 2 secured to the barrel, and a breech plate 3 which may be locked to the frame plate to constitute a closure for the breech end of the barrel. In the design illustrated in the co-pending application, a chamber plate 4 is provided between the frame plate 2 and breech plate 3, for convenience in supporting a chamber bushing and cartridge. A barrel sleeve 5 is slidable on the exterior surface of the barrel and may be secured to an action plate 6 engaged by springs 7 which urge-the action plate and thereby the barrel sleeve secured thereto to project in advance of the muzzle of the barrel. A guard% is conveniently mounted on the barrel sleeve to contain any matter displaced by the penetration of a fastener into the Work surface.

When the tool is placed in engagement with a work surface, it will be noted that it will be necessary to apply sufficient force to compress the springs 7 and permit the barrel to move forward in the barrel sleeve 5 before the muzzle of-the barrel can be brought into complete or near engagement with the work surface,as' shown in FIG. 1.

This relative movement between barrel and barrel sleeve is utilized to cock the tool for firing, by providingon the action plate 6, as best shown in FIG. 2, a rearwardly extending action bar 9'which is so supported that it may be projected, when the breech is closed andlocked, through aligned holes in the frame plate 2, breech plate 3 and chamber plate 4. g 1 a As'bestseen in FIG. 1, a breech housing 10 is suitably secured to the breech plate 3 and extends rearwardlytherefrom to enclose the firing mechanism and to support ahandle 11. Within the housing 10, a striker 12.is pro 3 vided with a firing pin or point of reduced diameter 13 so located as to properly impact the priming mixture contained in a cartridge chamberedin the barrel 1. To the rear of the firing pin point, the striker .12 cornprises'a section 14 having guiding engagement in an aperture in the breech plate, a section of further increased diameter 15 and a-section of maximum diameter 16 terminating in a forwardly facing shoulder 17. The striker also comprises a rearwardly extending shank18 receiving a striker. spring 19, the rear end of the shank entering a socket' abutment 20. secured in the rear faceof thebreech housing 10. -The striker 12 is thus'guidedfor: reciprocation along its longitudinal axis.by the socket 20 and by'the reception of the portion 14 in the apertured breech plate 7 and is urged forwardly in thosemembers by thespring .19.

As shown in FIG. 2,- an. action bar. extension 21 is:

supported in longitudinal alignment with" the aforemen; tionedaction bar 9. When the action bar 9 is supported by the barrel sleeve 5 in contact with a work surface.

and pressure is exerted on thehandle of the tool to bring the tool nearer to the work, it will'be'noted that the s 7 housing "10, plates 2, 3 and 4,1 and barrel 1 all move forwardly relative to the barrel sleeve 5 and the action'bar 9 will pass through the aligned apertures in the aforementioned plates into supporting engagement with the action bar'extensionzl which, as noted,has its forward end, supported in the apertured breech plate 3. Continued forward movement of the tool results in arearward displacement of the ,action bar extension within the advancing housing and relative to the breech; plate 3.

Ihe rear end 22 ,of'the action bar; extension 21 is received in a socket 23 secured in the housing it) and there abuts a spring pressed plunger 24 having the effect of restoring the action bar extension to a forward position in the housing when it is freed for such movement barrel'sleeve and the work surfac As shown in FIGS. 3, 4 and 6, secured rigidly to the action bar extension and projecting transversely therefrom is a two armed sear 25. One arm of .the sear defines a portionlfi whichis normally beneath and in supporting by rearwardretraction of the housing relative to the engagement with the forwardly facing shoulder 17 defined 'by,the maximum diameterlsection 16 of the striker. The action bar extension and sear assembly is urged to rotatably move said portion 26. toward the striker by suitable meansrsuch as a sear spring 27 formed to exertsuch rotary pressure withoutsubstantially impeding longitudinal movement of the action bar/sear assembly.

.7 When thetool housing isrnoved forwardly towards I work surface upon which the barrel sleeve is supported,

the sear will participate inthe relative motion of the.

7 action :bar extensioniabove referred to. 'Since the sear isinsupporting engagement with the shoulder 17 on the striken, thestriker also will participate in .that motion and-,willbevsupported in a rearmost position against the spring urged forwardly to an idle position;

'I'hus, innormal'operationof the tool, the exertionof adequate pressure on the handle will move the housing and parts associated therewithtoward a workpiece on V which the barrellsleeve'is supported and in consequence the -action bar extension and "striker will be'moved to their rearmost positions in the housing. In this position,

pulling the trigger rocks the sear lever, which rotates the sear out of supporting engagement with the striker and the cartridge firing movement thereof, This operation can only take place-when the tool' has been properly positioned and pressed against a work surface.

'Means which are not essential to the understanding of the present invention but whichare fully disclosed in the co-pending application are provided to earn the striker back far enough after a firing movement to permit the sear "to resume its. position. beneath the striker shoulder 17 I 'after'firing. Obviously, if the. pressure holding the'tool against the work is released prior'to pulling the trigger,

- 6 theactionbar extension, sear and striker return'to their dental firing of such a tool if dropped from a considerable height, as from a building scaflold.

If we assume that such a tool is dropped muzzle first from a substantial height. upon a resistant surface such as a concrete floor, it will be seen that the barrel, frame plate, breech plate and housing assembly, having substantial inertia, will advance toward the resistant surface,

while the barrel sleeve and parts associated therewith will be stopped, and this may result in cooking the striker spring. There have, been instances in which the resulting impact has jarred the sear from beneath the striker shoulder and permitted the tool to fire.

Similarly, if the tool should be dropped handle first the housing and barrel assembly will be stopped on impact but theguard, barrel sleeve, action plate, action bar,

action bar extension and sear, all have substantial inertia and may exert sufficient force to cock the striker spring. In this instance also inertia forces are acting to move the trigger in the sear releasing direction and if the proper timesequence of movements happens to occur it is possible for the tool'to fire.

Although instances in whicltaccidental firing of such tools may be attributed to this cause are few and far between, the possible consequences of an accidental firing H are too tragic to permit ignoring the risk when a remedy is available. 1 By utilizing one of the bolts 34, which secure housing 10 to the breech plate 3, we have found that we can mount an inertia block for sliding'movement along a line parallel to ltheaxis of the barrel. Preferably this inertia block is balanced in an intermediate rest position by supporting it between coil springs 36 and 37.both rcceived on the shank of the cover bolt 34 and engaged respectively between the rear face of the breech plate and the front face of the inertia block 35 and between the rear face of the inertia block 35 and a boss 38 in the housing 10 through which the cover bolt 34 passes.

' The mounting of this inertia block is best seen in FIG. 5,

whileits functioning will be best understood by reference to FIGS.'7 8, 9 and 10.

The inertia block 35, as seen in FIG. 6, is formed to I define aflat side 39 in g iding engagement with the inside 7 which would effect that cockin of the housing and with a circumferentially extending groove40'separating two portions 41 and42 of maximum diameter respectively in front'of and behind the groove 40. The location of the groove 40 is so selected and the grooveis'of such widthanddepth that, with the inertia block in'its balanced position of rest and with the tool cooked in readiness to fire as previously set forth, an extension 43 on the sear 25 is opposed to the, groove 40 and may swing therethrough when pulling the trigger fingerpiece 33 actuates the sear lever 29 to engage the sear arm 28. This isthe position illustrated in FIG. 8. a

In any situation in which the tool maybe'dropped muzzle first, there is, as pointed out previously, a possibility that the striker spring may be cocked but the forces g will result in a relatively forward .displaeementof the inertia block 35, asseen in foremost position in the housing, and the .tool' does not remain cockedfor firing as a function of pulling the trigger o y. 7 I j The mechanism'thus' far described is shown in detail in the co-pendingapplicafion above referredto andis shown in .a more rudimentary form and claimed in the patent above referredto. The presentinvention' adds to' the mechanism. above described a few simple components which ,willnowbe described and which prevent the acci- V FIG.,9, compressing'the forward spring 36 and bringing the rearward large diameter portion 42 of the inertia block into movement blocking opposition to the sear extension 43. Thus, even though the fall may have been accompanied by jarring forces which would otherwise disengage the sear, the inertia block moves automatically to a position which blocks such disengagement and will remain in that position until rebound from the surface upon which the tool has been dropped releases the cocking of the striker spring.

Similarly, .if the tool is dropped handle foremostfthe l striker spring may be'cocked as n'oted above and in this case inertia forceswill cause a rearward displacement of the inertia block against the urging of spring 37, as shown in FIG. 10, and will bring the front large diameter portion 41 of the inertia block into movement blocking opposition to the sear extension 43.

Thus, in either case in which drop firing of the tool is a possibility, the inertia block functions to prevent jar oil of the sear and eliminates the chance of injury.

Although we have here shown and described a very specific embodiment of our invention, it will be obvious that many variations of the principles here enunciated are possible. Accordingly, we wish it to be understood that we consider the scope of our invention to be limited only by the claims appended hereto.

What is claimed is:

1. In a powder actuated tool, having a barrel, a striker which is spring urged for movement to fire a power load chambered in the barrel, and striker controlling sear means manually movable to a position to release said striker for power load firing movement, a device for preventing drop firing of the tool due to any component of a force acting in either direction along a line parallel to the axis of the barrel, said device comprising an inertia block reciprocable along a line parallel to the axis of the barrel, balanced resilient positioning means opposing movement of said inertia block in either direction away from a position of rest, and means on said inertia block moved into movement blocking opposition to said striker controlling sear means whenever said inertia block has been substantially displaced from said position of rest.

2. The device described in claim 1, said inertia block comprising a member of substantial mass said means on the inertia block being defined by portions of said block having such lateral dimensions that when they are opposed to the path of movement of the striker controlling sear means the sear means will engage one of said end portions before movement thereof is completed, said end sections being separated by a section of cross-sectional area so reduced that when it is opposed to the path of movement of the sear means movement of the sear means can be completed to release the striker without engaging said inertia block, said section of reduced cross-sectional area being so positioned on the inertia block as to be opposed to the path of movement of the sear means only when the inertia block is in its balanced position of rest.

3. The device described in claim 2, said inertia block being provided with a longitudinally extending bore, said inertia block being supported for reciprocating movement on a longitudinally extending support bolt mounted in axial parallelism with the axis of the barrel and passing through said bore.

4. In a powder actuated tool, having a barrel, a striker which is spring urged for reciprocating power load firing movement along a line parallel to the axis of the barrel, and striker controlling sear means movable-in a plane generally transverse to said line to release said striker, a device for preventing drop firing of the tool comprising an inertia block reciprocable along a line parallel to the axis of the barrel, balanced resilient positioning means opposing movement of said inertia block in either direction away from a position of rest, a section of said inertia block of reduced cross section between the ends of said inertia block which section in said position of rest of the inertia block is opposed to the direction of transverse movement of said sear means and provides clearance to permit striker releasing movement thereof, the portions of said inertia block adjacent the ends thereof being of such lateral dimensions relative to the axis of reciprocation of said inertia block as to extend into the path of transverse movement of said sear means and prevent striker releasing movement thereof when said inertia block has been substantially displaced in either direction along the line of reciprocation away from said position of rest.

5. In a powder actuated tool, having a barrel, a barrel sleeve telescoped over said barrel and spring urged to project in advance of the muzzle of said barrel, a striker spring urged toward said barrel for firing a power load chambered in the barrel, sear means movable in a plane at right angles to the axis of the barrel and releasably engaged with said striker to manually control the release of said striker, and action bar means coupling said barrel sleeve to said sear means to move said sear means and said striker in a direction parallel to the axis of the barrel to a cooked position as said barrel is advanced within said barrel sleeve toward a work surface with which said barrel sleeve is engaged, a device for preventing drop firing of the tool comprising an inertia block mounted with capacity for longitudinal movement along a line parallel to the axis of the barrel, balanced resilient positioning means acting on opposite ends of said inertia block and yieldingly opposing movement of said inertia block in either direction away from a position of rest, and means on said inertia block brought into movement blocking opposition to said sear means whenever said inertia block has been substantially displaced from said position of rest.

6. The device described in claim 5, said inertia block being provided with a longitudinally extending bore, said inertia block being supported for longitudinal movement on a support bolt axially parallel to the axis of the barrel and passing through said bore in the inertia block.

7. The device described in claim 6, said inertia block comprising a member of substantial mass, said means on said inertia block being defined by substantially identical end portions of such lateral dimensions that whenever either end portion is moved into opposition with the plane of striker releasing movement of the sear means the sear means will engage one of said end portions before such releasing movement can be completed, said end sections being separated by a section of reduced cross-sectional area so'laterally dimensioned that when it is in opposition with the plane of striker releasing movement of the sear means releasing movement of the sear means can be completed without engaging said inertia block, said section of reduced cross-sectional area being so longitudinally positioned on said inertia block and of such longitudinal extent as to be opposed to the plane of striker releasing movement of the sear means only when the inertia block is in its balanced position of rest.

No references cited. 

